Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
ACETAMINOPHEN AND CODEINE PHOSPHATE vs FARESTON
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Acetaminophen: centrally acting analgesic and antipyretic, possibly via inhibition of cyclooxygenase (COX) and modulation of cannabinoid receptors. Codeine: prodrug converted to morphine; mu-opioid receptor agonist.
Selective estrogen receptor modulator (SERM) that competitively binds to estrogen receptors, exerting antiestrogenic effects in breast tissue.
Mild to moderate pain,Pain accompanied by fever
FDA-approved for the treatment of metastatic breast cancer in postmenopausal women with estrogen receptor-positive tumors,Off-label: treatment of advanced breast cancer in premenopausal women in combination with ovarian suppression
One or two tablets (acetaminophen 300 mg/codeine 30 mg per tablet) orally every 4-6 hours as needed for pain; maximum 12 tablets daily.
60 mg orally once daily.
Acetaminophen: 2–3 hours (prolonged in hepatic impairment). Codeine: 2.5–3.5 hours; metabolites: morphine 1.5–2.5 hours, codeine-6-glucuronide 3–4 hours. Clinical context: dosing interval every 4–6 hours.
The terminal elimination half-life of toremifene is approximately 5 days (range 2-10 days). The half-life of its main metabolite, N-desmethyltoremifene, is about 11 days. This long half-life supports once-daily dosing.
Acetaminophen: primarily glucuronidation and sulfation in liver; minor CYP450 (CYP2E1) to toxic NAPQI. Codeine: CYP2D6 to morphine; CYP3A4 to norcodeine; glucuronidation.
Primarily hepatic via CYP3A4 and CYP1A2; undergoes glucuronidation; active metabolite N-desmethyltoremifene
Acetaminophen: renal elimination of conjugated metabolites (glucuronide 60%, sulfate 30%, cysteine/mercapturate <5%), less than 5% unchanged. Codeine: renal elimination of codeine (5–15%), morphine (5–10%), norcodeine (10–20%), and conjugates; 90% excreted in urine within 24 hours.
FARESTON (toremifene) is extensively metabolized in the liver. Excretion is primarily fecal (approximately 70%) with renal excretion accounting for less than 10% of the dose as unchanged drug and metabolites.
Acetaminophen: 10–25% (albumin). Codeine: 7–25% (primarily albumin).
Toremifene is >99% bound to plasma proteins, primarily albumin.
Acetaminophen: 0.9 L/kg. Codeine: 3–6 L/kg (extensive tissue distribution).
The apparent volume of distribution (Vd) is approximately 580 L (about 8 L/kg for a 70 kg individual), indicating extensive tissue distribution.
Oral: acetaminophen 88% (variable first-pass); codeine 50–60% (first-pass metabolism to morphine, norcodeine, and conjugates).
Oral bioavailability of toremifene is not precisely determined but is estimated to be nearly 100% based on absorption and first-pass metabolism studies.
GFR 30-50 m L/min: administer every 6 hours; GFR 10-29 m L/min: administer every 8 hours; GFR <10 m L/min: administer every 12 hours; hemodialysis: not recommended.
No dose adjustment required for GFR ≥30 m L/min; insufficient data for GFR <30 m L/min.
Child-Pugh A: no adjustment; Child-Pugh B: reduce dose by 50% and extend interval to every 8 hours; Child-Pugh C: contraindicated.
Contraindicated in Child-Pugh class C; use with caution in class A or B without specific dose reduction guidelines.
For children ≥12 years: acetaminophen 10-15 mg/kg/dose and codeine 0.5-1 mg/kg/dose orally every 4-6 hours; maximum acetaminophen 75 mg/kg/day, codeine 6 mg/kg/day. For children <12 years: not recommended due to codeine safety concerns.
Safety and efficacy not established; no recommended dose.
Start with lowest effective dose; acetaminophen component maximum 3 g/day; consider reduced codeine dose (e.g., 15 mg) due to increased sensitivity and risk of respiratory depression; extend dosing interval to every 6-8 hours.
No specific dose adjustment; monitor renal function and electrolyte balance.
Risk of medication errors: confusion between milligram and milliliter doses, and between codeine and acetaminophen components. Contraindicated for postoperative pain management in children following tonsillectomy/adenoidectomy due to risk of respiratory depression and death.
None
Hepatotoxicity (acetaminophen overdose); respiratory depression; drug dependence; ultra-rapid metabolizers of codeine (CYP2D6) leading to morphine toxicity; concomitant CNS depressants; use in pediatric patients; avoid alcohol.
QT interval prolongation,Hypercalcemia in patients with bone metastases,Endometrial hyperplasia/cancer risk,Thromboembolic events,Ocular toxicity (dose-dependent retinopathy),Tumor flare
Hypersensitivity to acetaminophen or codeine; severe respiratory depression; acute or severe asthma; paralytic ileus; post-operative pain management in children after tonsillectomy/adenoidectomy; breastfeeding (in ultra-rapid metabolizers); concomitant MAOIs.
Hypersensitivity to toremifene or any excipients,History of thromboembolic disease,Pre-existing endometrial hyperplasia,Patients with long QT syndrome or concurrent use of QT-prolonging drugs
Avoid alcohol; high-fat meals may delay absorption but not clinically significant.
Avoid grapefruit and grapefruit juice due to CYP3A4 inhibition, which can increase toremifene levels and risk of adverse effects. No other significant food interactions known. Take with or without food.
Acetaminophen is considered low risk in all trimesters at therapeutic doses; chronic high doses may be associated with adverse outcomes. Codeine is associated with risk of respiratory depression and neonatal withdrawal if used near term; may cause neural tube defects and other malformations with first-trimester exposure, but data are conflicting. Use lowest effective dose for shortest duration.
Pregnancy Category D. First trimester: Risk of fetal harm, including spontaneous abortion and congenital malformations (e.g., craniofacial, cardiac). Second and third trimesters: Potential for fetal hypothalamic-pituitary-gonadal axis disruption, ambiguous genitalia in female fetuses, and other adverse effects based on animal studies.
Acetaminophen is excreted into breast milk in low amounts (M/P ratio ~0.91-1.42) and is considered compatible with breastfeeding. Codeine is also excreted in breast milk; risk of infant opioid toxicity depends on maternal CYP2D6 phenotype. Ultra-rapid metabolizers may produce higher morphine levels. Use with caution, avoid in known CYP2D6 ultra-rapid metabolizers, and monitor infant for sedation and respiratory depression.
Not recommended during breastfeeding. Toremifene may be excreted in human milk; M/P ratio not established. Potential for serious adverse reactions in nursing infants, including hormonal disruption.
No routine dose adjustment needed for acetaminophen. Codeine pharmacokinetics are altered in pregnancy: increased clearance and volume of distribution may require dose adjustment; however, due to variability in CYP2D6 metabolism, individualize dosing and monitor for efficacy and toxicity. Avoid codeine in pregnancy unless alternative analgesics are ineffective.
No established dose adjustments; use contraindicated in pregnancy. Pharmacokinetic changes (increased volume of distribution, altered clearance) may require empirical dose reduction if used inadvertently, but no specific guidelines exist. Avoid use.
For acute pain, limit codeine to 3 days; avoid in children under 12 due to CYP2D6 ultra-rapid metabolizer risk of fatal respiratory depression; monitor for constipation; assess liver function for acetaminophen hepatotoxicity; use with caution in renal impairment.
FARESTON (toremifene) is a selective estrogen receptor modulator (SERM) used for metastatic breast cancer in postmenopausal women with estrogen receptor-positive tumors. Unlike tamoxifen, toremifene has a longer half-life (about 5 days) and may have a lower risk of thromboembolic events. Monitor liver function tests regularly due to potential hepatotoxicity. Prolongation of QT interval has been reported; avoid in patients with pre-existing QTc prolongation or with other QT-prolonging drugs. Use with caution in patients with endometrial hyperplasia or history of thromboembolic disease.
Take exactly as prescribed; do not exceed 4000 mg acetaminophen per day.,Avoid alcohol while taking this medication.,Do not use with other acetaminophen-containing products.,May cause dizziness or drowsiness; avoid driving until you know how you react.,Common side effects include constipation, nausea, and drowsiness.,Seek emergency if signs of allergic reaction or difficulty breathing occur.
Take this medication exactly as prescribed, usually once daily with or without food.,You may experience hot flashes, nausea, or sweating; these are common and usually manageable.,Report any unusual vaginal bleeding, discharge, or pelvic pain to your doctor immediately.,Watch for signs of blood clots such as leg pain/swelling, sudden chest pain, or shortness of breath.,Avoid grapefruit and grapefruit juice while on this medication as they may increase side effects.,Use non-hormonal contraception if you are still able to become pregnant; toremifene can harm a fetus.,Do not stop or change your dose without consulting your healthcare provider.
"Pirenzepine, a selective M1 muscarinic antagonist, reduces gastrointestinal motility and secretions, while codeine, an opioid agonist, also decreases gastrointestinal motility via mu-opioid receptors. Concurrent use leads to additive anticholinergic and opioid effects, resulting in enhanced risk of severe constipation, paralytic ileus, and central nervous system depression. Clinically, patients may experience exacerbated sedation, respiratory depression, and urinary retention."
"Ropinirole, a non-ergoline dopamine agonist used in Parkinson's disease and restless legs syndrome, may reduce the analgesic efficacy of codeine. This is likely due to pharmacodynamic antagonism at central dopamine and opioid receptors, as well as potential pharmacokinetic interactions that decrease the conversion of codeine to its active metabolite morphine via CYP2D6 inhibition by ropinirole. The resultant blunted opioid response can lead to inadequate pain control, necessitating dose adjustment or alternative therapy."
"Vemurafenib induces CYP3A4, significantly reducing the plasma concentrations of codeine, which is metabolized via CYP3A4 to its active metabolite morphine. This may diminish codeine's analgesic efficacy, potentially leading to inadequate pain control. Additionally, reduced formation of morphine may lower the risk of opioid-related adverse effects."
No interactions on record
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about ACETAMINOPHEN AND CODEINE PHOSPHATE vs FARESTON, answered by our medical review team.
ACETAMINOPHEN AND CODEINE PHOSPHATE is a Opioid Agonist that works by Acetaminophen: centrally acting analgesic and antipyretic, possibly via inhibition of cyclooxygenase (COX) and modulation of cannabinoid receptors. Codeine: prodrug converted to morphine; mu-opioid receptor agonist.. FARESTON is a Selective Estrogen Receptor Modulator that works by Selective estrogen receptor modulator (SERM) that competitively binds to estrogen receptors, exerting antiestrogenic effects in breast tissue.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between ACETAMINOPHEN AND CODEINE PHOSPHATE and FARESTON depend on the specific clinical indication. These are agents from distinct pharmacological classes and are not directly interchangeable by dose. A physician or clinical pharmacist should guide any therapeutic switching decisions.
The standard adult dose of ACETAMINOPHEN AND CODEINE PHOSPHATE is: One or two tablets (acetaminophen 300 mg/codeine 30 mg per tablet) orally every 4-6 hours as needed for pain; maximum 12 tablets daily.. The standard adult dose of FARESTON is: 60 mg orally once daily.. Dosing should always be individualized based on indication, renal and hepatic function, age, and other patient factors.
No direct drug-drug interaction has been formally documented between ACETAMINOPHEN AND CODEINE PHOSPHATE and FARESTON in current clinical databases. However, individual patient risk factors including other medications, organ function, and comorbidities should always be evaluated by a qualified healthcare provider.
The maternal-fetal safety profiles differ. ACETAMINOPHEN AND CODEINE PHOSPHATE is classified as Category D/X. Acetaminophen is considered low risk in all trimesters at therapeutic doses; chronic high doses may be associated with adverse outcomes. Codeine is associated with risk of respirat. FARESTON is classified as Category C. Pregnancy Category D. First trimester: Risk of fetal harm, including spontaneous abortion and congenital malformations (e.g., craniofacial, cardiac). Second and third trimesters: P. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.